Vibrato system for musical instruments



June '7,v 1966 f J. A. LONG VIBRATO SYSTEM FOR MUSICAL INSTRUMENTS 4 Sheets-Sheet 1 Fled Oct. 3. 1963 ,N Lmxmmnwbnow June 7, 1966 J. A` LONG 3,255,297

VIBRATO SYSTEM FOR MUSICAL INSTRUMENTS Filed Oct. 5. 1963 4 Sheets-Sheet 5 June 7, 1966 J. ALONG VIBRATO SYSTEM FOR MUSICAL INSTRUMENTS 4 Sheets-Sheet 4 Filed Oct 5. 1965 n .mE

INVENTOR. James A. Long United States Patent O 3 255 297 vInRAro sYsfrEM non MUsrcAr. INSTRUMENTS .lames A. Long, Fort Wayne, Ind., assigner to The Magna vox Company, Fort Wayne, Ind., a corporation of Delaware Filed Oct. 3, 1963, Ser. No. 313,536 1S Claims. (Cl. Slt-1.25)

This invention relates generally to electrical musical instruments and more particularly to a system whereby a deep vibrato or tremulant effect can be obtained with musical instruments and particularly with electronicy organs.

For many years, electric organ manufacturers have endeavored to provide the most pleasing type of vibrato effect' possible with their instruments. Around 1945, a unit was invented which was called a Leslie, which is the name of the man to whom the invention is attributed. The Leslie gave the effect of a loud-speaker revolving on a Avertical axis. It was widely accepted in the electronic organ industry because it produced a very deep, pleasing, vibrato effect when an organ was played through it. v f

It had several drawbacks, however. A motor Was used to drive a revolving sound dellector which was placed below the stationary speaker. This motor requiredperiodic oiling. Because of the inertia of the revolving unit, it took` several rotations before normal speed was reached and, conversely, took several rotations to slow down and stop: This produced a very undesirable sound when turning off or on.

Because of the directional characteristics of the high frequency components of complex organ voices, the Leslie chopped them off, producing unsatisfactory performance on anything but flute type voices. This was and is an extremely important limitation on the Leslie unit.

Because of these drawbacks of the Leslie unit, many organ manufacturers have put substantial effort into obtaining electronic systems which could produce the desirable effects which the Leslie produced, without having the sameshortcomings as the Leslie unit and without having other shortcomings just as serious or more serious. I-Ieretofore, manufacturers have had little success and many, if not most of them, have retained the true Leslie unit.

It is, therefore, a general object of the present invention to provide non-mechanical means for producing a deep vibrato or tremulant effect in musical instruments, primarily electronic or electrical musical instruments including electronic organs.

A further object is to provide a system producing a desirable effect similar to that of the Leslie unit without `any undesirable effects.

A further object is to provide a system which tends to minimize the variation in apparent results which oc- A curs to a person who moves from place to place in a room.

A still further object is to provide a system which avoids intermodulation distortion when more than one musical note is played at a time.

Described briefly, in a typical embodiment of the present'invention, a music signal from the organ is fed into two output channels for two speakers disposed with their radiation axes at 90 from each other. The music signal in each channel is amplitude modulated at 6.5 cycles per second, but the peaks of the modulation envelopes in the first and second channels are separated lby 90 in time.

The music signal is also fed into a phase splitter which produces a 180 phase shift music signal which is fed into a matrix with the modulated music signals. The result is periodic cancellation of the signal in each of the two channels, with the cancellations occurring in o ne channel 3,255,297 Patented June 7, 1966 ICC ahead of the cancellations occurring in the other channel. When these signals are fed to the speakers, there is produced a Doppler effect resulting in a very desirable sound.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims.

FIG. 1 is a block diagram of a system according to a typical embodiment of the present invention.

FIG. 2 is a chart demonstrating typical wave forms at various locations in the system.

FIG. 2A is a continuation of the chart of FIG. 2. v

FIG. 3 is a schematic diagram of the electronic circuitry which may be incorporated in the typical embodiment.

FIG. 3A is a continuation of the schematic of FIG. 3.

Referring now to the drawings in detail, and particularly FIG. l thereof, a modulating vibrato signal is generated by the vibrato generator 21. This generator may take one of many possible well known forms and may produce various waveforms of any of several frequencies. It has been found that a sinusoidal waveform at a frequency of 6.5 cycles per second gives very satisfactory results. The generator output at conductor 1 in FIG. l is shown in FIG. 2 on the line identified 2-1. This output is fed through two phase-shift networks 22 and 23 and their outputs at conductor 2 and conductor 3, respectively, are shown on the lines 2-2 and 23 in FIG. 2. The waveform from phase-shift network 22 leads the input waveform from the vibrato generator by 45 and the waveform from the phase-shift network 23 lags the waveform from the vibrato generator by 45 The net phase difference between the outputs of the phase-shift network 22 and phase-shift network 23 is 90. The output signals from the phaseshift networks 22 and 23 are fed to modulators 24 and 2 6 for two channels which will be hereinafter referred to as channels A and B.

Referring back to FIG. l, a music signal from an electronic or electrical musical instrument 27 such as an electric organ, for example, is fed on the conductor 4 to a phase splitter 28. The waveform prodced by the musical instrument 27 Iand appearing on conductor 4 may be characterized as shown on the line 2-4 in FIG. 2. The outputs yare taken from the phase splitter. On the rst output line or conductor No. 5, a signal which can be termed the plus X signal is produced and is of the same phase as the input signal from the musical instrument on conductor 4. On output conductor 6, the signal is like that on conductor 5 except for the fact that it is reversed in phase It Iwill be referred to hereinafter as the minus X signal. These two signals on conductors 5 and 6 may be represented as shown on lines 2-5 and 2-6, respectively, in FIG. 2.

The plus X signal is fed to the modulator 24 for the A channel and also to the modulator 26 for the B channel. In each of these modulators, the plus X signal is modulated by one of the two 6.5 cycle signals previously shown yon line 2-2 in FIG. 2 and 2-3 in FIG.- 2. The result is to produce output waveforms on the lines 7 and 8 from the modulator 24 and the modulator 26, respectively, which can be represented -as shown on the lines 27 and 2-8 in FIG. 2. Because of the 90 phase difference in the two 6.5 cycle modulating signals, the peaks of Imodulation of the modulator outputs are displaced in time by 90. A

The two amplitude modulated signals appearing on the conductors 7 and 8 are fed to matrix networks 29 and 31 of channels A and B, respectively. Also, the unmodulated minus X signal on line 6 is also fed to each of thematrix networks. In the matrix, means are provided for adjusting the modulated signals of the two channels so that the average amplitude of each is equal to the constant amplitude of the phase reversed minus X signal. Therefore, during every half cycle of modulation, the modulated plus X signal and the unmodulated minus X signal for an instant will be exactly equal in amplitude and, being of opposite phase, will be cancelled out. At any other time during the modulating cycle, either the plus X signal or the minus X signal Will be larger than the other and will appear at the inputs on lines 9 and 10 of the channel A amplifier 32 and channel B amplifier 33, respectively. Examples of these waveforms into the channel amplifiers are shown on lines 2-9 and 2-10 in FIG. 2A. Because of the 90 phase difference between the signals in the A and B channels, the cancellation points of the signals into the channel amplifiers are displaced in time by 90.

The channel amplifiers 32 and 33 are high quality audio amplifiers and the signals are unchanged in passing through them except for amplitude increase. In output of channel amplifier 32 on line 11 is fed to the loudspeaker 34. The output of the channel B amplifier 33 is fed on line 12 to the loud-speaker 36. The nal composite signals to speaker 34 may be represented as shown on line 2-11 in FIG. 2A and the final composite signal to the speaker 36 may be represented as shown in line 2-12 of FIG. 2A.

Referring to these speaker input signals on lines 2-11 and 2-12 in FIG. 2A, it is to be noted that at time t equals 1, the signal in channel A is at its peak amplitude whereas at the same instant the signal in channel B is at zero. At time passes toward t=2, the signal in the A channel amplifier output decreases in 4amplitude while the signal in the B channel amplifier output increases in amplitude. At the time t=2, the signal in the A channel amplifier output is at zerovand ready to switch from plus X phase to minus X phase. At the same instant, the signal in the B channel amplifier output is at peak value in the plus X phase and is ready to decrease as time passes toward t=3. At time t=3, the signal in the A channel amplifier output is at a maximum in the minus X phase and ready to decrease to zero again at time z'=4. At the same time t=3, the signal in the B channel amplifier output is at zero and ready to switch to the minus X phase and increase to the maximum value at t=4. At the time t=4, the whole cycle begins to repeat.

The final effect is produced when the sound resulting in the A channel speaker 34 and B channel speaker 36 is projected on radiation `axes lwhich are disposed at 90 with respect to each other. In FIG. 1, the speakers are shown schematically in a position such that their axes of acoustical radiation subtend an arc of 90. These speakers are fixed in this relationship. No moving parts are associated therewith.

Consider now the application of the signals appearing on lines 2-11 and 2-12 in FIG. 2A to the loudspeakers 34 and 36, respectively, of FIG. 1. As the signal in the A channel speaker reaches its peak output and starts to decrease, the signal in the B channel speaker starts to increase in output, thereby causing a gradual shift of energy from one speaker to the other. As the ouput from the A channel speaker decreases to zero, the output in the B channel speaker reaches a maximum. Now if there were a third and fourth channels similar to the A and B channels and speakers at every 90 point, we could continue on around a 360 rotation with the energy gradually shifting from one speaker to the next lin 90 rotation steps. However, the same effect (as far as the ear is concerned) is obtained according to the present invention. For example, the effect of a third speaker located 180 away-from speaker 34 is obtained by reversing the phase of the musical signal and feeding it to the speaker 34 again. The output of speaker 34 thereby increases in amplitude as that ofthe speaker 36 decreases. Then as the output of the speaker 34 again passes its peak in this phase, the phase reversed signal being fed to the speaker 36 increases in output in the same phase as that of the signal now in the speaker 34. Thisv gives the effect of a fourth speaker displaced 180 from the speaker 36. As the A channel speaker 34 raises again in its output of a signal that is of the same phase as originally, one apparent full rotation of radiated acoustical energy has been completed and a new apparent rotation begins.

Because the modulation frequency selected is 6.5 cycles per second, the apparent full rotation of radiated acoustical energy occurs 6.5 times per second. If desired, other vibrato rates lmay be used if desired, to give variation in the iinal effect. At present, it appears that the range of 5 to 8 cycles per second seems to be the most acceptable lrange within which to select a vibrato rate to give the desired final effect.

Further with reference to FIG. 1, an additional speaker 37 is disposed between the speakers 34 and 36 and has its radiation axis on a line bisecting the angle between radiation axes of the speakers 34 and 36. The music signal from the musical instrument 27 and appearing on line 2-4 in FIG. 2 is fed to the amplifier y38 for the channel C whose output on conductor 13 is supplied Ito the speaker 37. The typical waveform of the sign-al input to the C channel speaker 37 may be represented as shown in line 2-13 of FIG. 2. The output of the C channel speaker, which is not modulated by the 6.5 cycle signal, blends in with the modulated signals from the A and B channel speakers and gives a more pleasing overall chorus effect.

Referring now to FIG. 3, two purposes are to be se-rved. The first is to disclose the novel modulator incorporated according to the present invention. The other is to provide an example of a working arrangement of circuit components, though it should -be understood that other arrangements m-ay also lbe employed which are within the scope of the present invention.

Referring -first to the novel modulator of the invention, two modulators are shown, modulators being required `for each channel. The modulator Iand its driver for the channel A are shown in block 24 and the modulator and its driver for `the channel B are shown in block 26. Both modulators are identical so only that for channel A will be described in detail.

The modulator includes an input conductor 2 for the 6.5 cycle per second modulating signal. It also includes an input line 5 for the music signal. Its output is at line 7. Between the music sig-nal input line 5 and the modulator output line 7, there is a light dependent resistor 41.

The light dependent resistor may be a light sensitive cadmium-sulphide photo cell. An example of the performance of Vsuch a cell is a change of resistance of from 10 megohms in total darkness to less than 200 ohms at high light levels. `In the circuit of the present invention, the point of operation is at about 4700 ohms, determined by the average or quiescent light level :of a #49 pilot lamp 49 which illuminates the light dependent resistor 41.

Because lthe light dependent resistor [is connected between -the music signal Iinput and the modulator output, the music signal passing through the resisto-r and appearing on output line 7 will be amplitude modulated if a variation of brightness occurs lin the pilot lamp 49. The 6.5 cycle modulating input signal on line 2 is -advanced 45 by phase shifter 22 and fed to the PNP transistor 44 which drives the PNP transistor 46 to modulate the brightness of the pilot lamp 49 in the collector lead of the transistor 46. Thus it is seen that the 6.5 cycle A.C. modulating signal causes the light output of the incandescent pilot lamp 49 to vary around an average output determined by quiescent D C. current through the lamp.

It has been seen that the light dependent resistor places a varying series impedance to the plus X signal derived on line 5 from the phase splitter 28. A resistance 50 is shown connected across the output (FIG. 3A) lines 7 and 8. This resistance has a variable tap 51 to ground 52.

Consequently, with a portion -of 4the resistance 50 producing a voltage divider action, amplitude modulation of the signal on line 7 results.

Because the output of the other modulator [for channel B is also connected to the resistor 50, and because the tap 51 to yground is movable, this affords a balance control for the two channels.

The minus X signal -is derived on line 6 from the phase splitter is Ifed through resistance 53 (FIG. 3A) to the channel A modulator output line 7. In like manner, the minus X signal is fed through a like resistor 54 to the output line 8 of the B channel modulator. The balance control 51 also influences the relative effect which the minus X signal has on the two channels. It might be mentioned at this point that the 'resistance of resistors 53 and 54 are selected to approximately equal lthe average resistance of the light dependent resistors.

The output `of the matrix for channel A on line 9 is the composite signal sho-wn in line 2-9 of FIG. 2A and the output of the matrix for the lB channel is as represented on the line 2-10 in FIG. 2A. These outputs are fed to the audio amplifiers32 and 3-3 respectively.

It is obvious from FIG. 3A that the input line 7 to the matrix is the same conductor as the output line 9 from the matrix. `It follows that the waveform 2-9 of FIG. 2A, and not waveform 2-7, actually exists on line 2-7.

Waveform 2-7 is that which would appear at the top of Y resistor 50 if the connection between lines 7 and 9 were broken.

Normally, in order to perfectly balance the matrix, lthe resistors 53 and -54` are fixed in value and the average `resistance of the light dependent resistors in each of the mod- Iulators is adjusted by setting the direct current through the pilot lamps therefor by use of the potentiometers 56 and 57 in the two modulators. y

Certain other parts of `the system shown in the schematic of FIG. 3 will now be described briefly. The power supply 48 receives a 110 volt alternating current input at the line plug 61. It provides negative direct current supply potentials on various outputs. For example, hegative potentials Iof 36 volts, 31 volts, 22 volts, and 16 volts are provided on the conductors 62, 63, 64, and 66 respectively. Because other regulated power supplies may also be used,

it is not believed necessary to describe the various components or their values.

As was mentioned previously, the vibrato generator may take any one of a variety of forms. The one illustrated on FIG. 2 is, therefore, merely an example. Two signals are fed into the vibrato generator on the lines 67 and 68 and are mixed at the junction `69 between the resistors 71 and 72. These signals have a difference or beat frequency of the desired modulation signal, and in this example it is 6.5 cycles per second. The signals may be obtained from the tone generators of the electrical musical instrument, if desired, and for this reason the two v lines 67 and 68 are connected to the block 27 representing the musical instrument.

The 6.5 cycle signal is filtered to the point where it is a satisfactory sine wave for use as a vibrato signal. At the output-of transistor 73, the signal appears on line 1 which is connected to the inputs of the two phase shifters 22 and 23. The signal on line 1, as mentioned previously, may appear as shown on the line 2-1 in FIG. 2. The output of each phase shifter is coupled to the driver and modulator for the corresponding channel wherein the emitter follower driver receives, on its base electrode, the output from the phase shifter.

The out-put of the modulator to .the matrix and from the matrix to the audio amplifiers has been discussed. Each of the audio amplifiers is shown schematically in FIG. 3A. Other audio amplifiers may also be found satisfactory and the function of that shown is conventional. Consequently, it will not be described in detail.4

Referring `now tothe amplifier and depth control in FIG. 3, the music signal output from the electrical musical instrument 27, and which may be derived from the organ output amplifier, for example, is coupled to the amplifier transistor 74. There it is amplified and passes through the emitter follower 76. It is then coupled on the line 77 to the control head 78 which includes a switch member 79 for use by the organist. There are three positions shown forthe control switch 79, these three positions being identified as full, medium, and of`r`. The movable contact 79 of the switch is connected to one end of the master gain control resistor 83, the other end of which is connected to ground. The movable tap of resistor 83 couples the signal through line 4 to the input of the phase splitter 28. The master gain control is for adjustment of the overall gain of the system.

Further detailed description of various elements and operations of the schematic of FIG. 3 is believed unnecessary, as they will be readily understood by those skilled in the art. Examplesof the nature and values of various components shown are as follows:

Resistors 71, 72, 84, 86 100,000 ohms. Resistor 87 1.5 megohm. Resistor 88 330,000 ohms. Resistors 89, 91 12,000 ohms. Resistor 92 1,800 ohms. Resistors 93, 94, 98 47,000 ohms. Resistors 96, 54, 53, 97 4,700 ohms. Resistor 99 3,900 ohms. Resistors 101 6,800 ohms. Resistors 102, 103, 104, 111 10,000 ohms. Resistors 106, 107 1,200 ohms. Resistors 108, 109 150 ohms. Resistors 112, 113 680 ohms. Balance Resistance 50 15,000 ohms. Resistors 116 12,000 ohms. Resistors 117 8,200 ohms. Resistors 118, 119, 121, 56, 57 1,000 ohms. Resistors 122 l0 ohms. Resistors 123, 124, 137 270 ohms. Resistors 126, 127, 128, 129 3.3 ohms. Resistors 131 330 ohms. Resistors 132, 133 .47 ohms. Resistors 134136 22,000 ohms. Resistors 138, 139 18,000 ohms. Capacitors 141, 142, 143 0,1 mfd. Capacitors 146, 147, 148, 149, 151, 166,

167 2O mfd. Capacitor 152 60 mfd. Capacitors 153, 154 '5 mfd. Capacitors 156 0.2.2 mfd. Capacitors 157, 158, 159 50 mfd. Capacitors 161, 162 100 mfd. Capacitors 163 .001 mfd. Capacitors 164 250 mfd. Capacitors 168 300 mfd. Master gain control 83 15,000 ohms. Transformers 171 5:1 ratio. PNP Transistors 70, 73, 44, 74, 76, 2N508.

PNP Transistors 46, 130, 140 2N301A. PNP Transistors 2N270. Silicon diodes 1N9l4. Light dependent resistors 41 Ferrox Cube Type 03.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. A vibrato system for an electrical musical instrument comprising: first and second signal channels; input means for a vibrato signal; first phase shifting means in said first channel and coupled to said input means, and second phase shifting means in said second channel and coupled to said input means, said first phase shifting means producing an output signal in said first channel displaced in time ahead of the output signal in said second channel by a predetermined amount; means producing a music signal; first modulating means in said first channel and coupled to said first phase shifting means and coupled to said music signal producing means and producing a first modulated music signal; second modulating means in said second channel and coupled to said second phase shifting means and coupled to said music signal producing means and producing a second modulated music signal; phase changing means coupled to said music signal producing means and producing a music signal delayed in time with respect to the music signal produced by said music signal producing means; matrix means receiving the time delayed music signal and receiving the said first modulated music signal and producing in said first channel a first composite output signal in said first channel which is a composite of said first modulated music signal and said time delayed music signal, and said matrix means receiving the time delayed music signal and receiving the said second modulated music signal and producing a second composite output signal in said second channel which is a composite of said second modulated music signal and said time delayed music signal, the first composite output signal being displaced in time from the second composite output signal; first speaker means coupled to said first channel and second speaker means coupled to said second channel, said speakers being oriented to dispose their principal sound radiation axes in different directions.

2. A system as set forth in claim 1 wherein said first phase shifting means and said second phase shifting means advance and retard in time, respectively, by amounts of 45, the output signals thereof, with respect to the time of the modulating signal input thereto; and wherein the time delayed music signal coupled -to said modulating means is 180 out of phase with the music signal coupled to the matrix means,` whereby periodic increases and' decreases of the output of each speaker are obtained, and the maximum output of one speaker is delayed in time from the maximum output of the other speaker by one quarter of a cycle.

3. The system as set forth in claim 1 and further comance means, said music signal input means being coupled Ito said music signal producing means and said light dependent resistance means providing a linear modulation of said music signal output in response to the periodically changing modulating signal input to the control electrode of said electronic discharge device.

6. A system as set forth in claim 5 and further comprising: manual control means coupled between said music signal means and said modulating means and between said music signal means and, said phase changing means accommodating manual control of the strength 'of the music signals coupled to said modulating means and to said phase changing means.

7. A system as set forth in claim 5 wherein au adjustable voltage divider is coupled between saidsecond and first channels in said matrix means.

8. A vibrato system for an electrical music instrument comprising; first and second signal channels; input means for a vibrato signal; first phase shifting means in said first channel and coupled to said input means, and second phase Shifting means in said second channel -and coupled to said input means, said first phase shifting means producing an output signal in said first channel displaced in time ninety degrees ahead of the output signal in said second channel; means producing a music signal; first modulating means in said first channel and coupled to said first phase shifting means and coupled to said music signal producing means and producing a first amplitude modulated music signal; second modulating means in said second channel and coupled to said second phase shifting means and coupled to said music signal means and producing a second amplitude modulated music signal; phase reversing means coupled to said music signal means and producing a phase reversed music output; matrix means receiving the phase reversed music signal and receiving the said first modulated music signal and producing a first composite output signal in said first channel which is a composite of said first modulated music signal and said phase reversed music signal; and said matrix means receiving the phase reversed music signal and receiving the said second modulated music signal of said second channel and producing a second composite output signal in said second channel which is a composite of said prising adjustable means in said first modulating means whereby the modulated music signal output of said first modulating means is adjusted so that its average amplitude is equal -to the constant amplitude of the time delayed music signal from said phase changing means whereby the first modulated music signal and the time delayed music signal will at one instant during every half cycle of modulation be of equal amplitudes and opposite phase, for cancelling each other periodically.

4. The system set forth in claimy 1 wherein said modulating means in one channel includes: a light dependent resistance means, with said music signal being coupled to said light dependent resistance means and to the output of said modulating means; an illuminating device; an electronic discharge device in circuit controlling said illuminating device, said illuminating device providing light received by said light dependent resistance means, and said electronic discharge device having a control electrode coupled to the phase shifting means of said one channel.

5. The system as set forth in claim 1 wherein said modulating means comprises: an illuminating device and an electronic discharge device in series with a source -of potential; a control electrode in said electronic discharge device; adjustable bias means coupled to said control electrode, said control electrode being coupled to said phase shifting means whereby a periodically changing signal applied to said control electrode modulates the light output of said illuminating means; music signal output means; light dependent resistance means receiving illumination from said illuminating means; music signal input means coupled to said light dependent resistsecond modulated music signal and said phase reversed music signal, the first composite output signal being displaced in time ninety degrees ahead of said second composite output signal; composite signal amplifier means coupled to each of said channels and amplifying the composite signals thereof; a first speaker coupled to the amplifier means for said first channel and a second speaker coupled to the amplifier means for said second channel, said speakers being oriented to dispose their principle sound radiation axes subtending an arc of ninety degrees. v

9. A system set forth in claim 8 wherein each of said modulating means comprises: an electronic discharge device having a load circuit; illuminating means in said circuit; an output; a light dependent resistor coupling said output to said music signal means, said resistor being illuminated by said illuminating means; the output signal of one of said phase shifting means being coupled to a control electrode of said electronic discharge device to vary illumination of said light dependent resistor in response to said output signal to produce the amplitude modulation of said music signal.

10. A vibrato system for an electrical musical instrument comprising: first and second signal channels; input means for a vibrato signal; first phase shifting means in said first channel and coupled to said input means, and second phase shifting means in said second channel and coupled to said input means, said first phase shifting means producing routput signal in said first channel displaced in time ninety degrees `ahead of the output signal in said second channel; means producing a music signal; first modulating means in said first channel and coupled to said first phase shifting means and to said music signal means and producing a first amplitude modulated music signal; second modulating means in said second channel and coupled to said second phase shifting means and coupled to said music signal means and producing a second amplitude modulated music signal; phase reversing means coupled to said music signal means and producing a phase reversed music signal output; matrix means receiving the phase reversed music signal and receiving the said finst modulated music signal and producing a first composite output signal in said first channel which is a composite of said first modulated music signal and said phase reversed music signal,V

and said matrix means receiving the phase reversed music signal and receiving the said second modulated music signal of said second channel and producing a second composite output signal in said second channel which is a composite of said second modulated music signal and said phase reversed music signal, the first composite output signal being displaced in time ninety degrees ahead of said second composite output signal; composite signal amplifier means coupled to each of said channels and amplifying the composite signals thereof; a first speaker coupled to the amplifier means for said first channel and a second speaker coupled to the amplifier means for said second channel, said speakers being oriented to dispose their principal sound radiation axes subtending an arc of ninety degrees; anda third speaker disposed with its principle sound radiation axis bisecting the angle subtended by the said. axes of said first and second speakers; and means coupling the music signal from said music signal producing means to said third speaker.

11. In an electronic system, the combination comprising: a source of music signals; phasing means coupled to said source and producing phase separated music signals at separate outputs; a first input conductor connected to one of said outputs to receive music signals to .be modulated; an output conductor for a modulated music signal; a second input conductor for a modulating signal; a light dependent resistor connected in circuit between said first input conductor and said output conductor; an electronic discharge device having a control element coupled to said second input conductor; an illuminating device illuminating said resistor and controlled by said electronic discharge device and providing controlled illumination of said resistor to Vary the illumination thereof to modulate sign-a1 coupled to said first input conductor.

12. In an electronic system, the combination comprising: a source of music signals; phasing .means coupled to said source and producing at first and second outputs, music signals separated in ph-ase by 180 degrees; a pair of modulators, each modulator comprising: an input conductor connected to said first output for a music signal to be modulated; an output conductor for a modulated signal; a light dependent resistor connecting said conductors in series circuit relationship; an electronic discharge device having a control circuit and a load circuit; an illuminating device in said load circuit, sad illuminating device providing light received by .said

light dependent resistor, the light output thereof being controlled by a modulating input signal coupled to said control circuit, to provide a modulated signal at said output conductor.

13. In an electronic system, the combination comprising: a source of music signals; phasing means coupled to said source and producing said music signals at a first output and inverted music signals at a second output; a modulator comprising: a first input conductor connected to said first output, for a signal to be modulated; an illuminating device and an electronic discharge device in series relation-ship across a source of potential; a second input conductor for a modulating signal; a control electrode in said electronic discharge device, said control electrode being coupled to said second input conductor for a modulating signal input whereby a signal of varying amplitude applied to said control electrode varies the light output of said illuminating device; and a light dependent resistor receiving illumination from said illuminating means, said light dependent resistor being connected to said first input conductor and to a modulator output conductor and providing a resistance to said signal to be modulated, said resistance varying with the said light output and thereby variably attenuating the signal in said first input conductor and providing a modulated music signal output on said modulator output conductor in response to the modulating signal input to the control electrode of said elec-- tronic disch-arge device; said modulator output conductor and said second output of said phasing means being connected to matrix means mixing said inverted music signal with said modulated music signal to4 produce a composite output signal.

14. Apparatus producing a vibrato musical effect and comprising: means modulating a music signal in a first channel at a selected modulation frequency; means modulating the same music -signal in a second channel at the same modulation frequency and at a fraction of a modulation signal period after the modulation in the first channel; means inverting the music signal; means mixing the inverted music signal with the modulated signals in each channel and producing a composite signal in each channel; first and second speakers; means coupling the composite signal in one channel to said first speaker; and means coupling the composite signal in the other channel to said second speaker; said second speaker being disposed with its radiation axis at an angle with respect to the radiation axis of said first speaker.

15. Apparatus producing a vibrato musical effect land comprising: means modulating a music signal in a first channel at a selected modulation frequency; means modulating the same music signal in a second channel at the same modulation frequency and at a quarter of a modulation signal periodafter the modulation in the first channel; means inverting the music signal; means mixing the inverted music signal with the modulated signals in each channel and producing a composite signal in each channel; means for adjusting the modulated signals of said channels to establish =a desired relationship between average amplitude of each of said modulated signals and the amplitude of said inverted music signal; first Iand second speakers; means coupling the composite signal in one channel to said first speaker; and means coupling the composite signal in the other channel to said second speaker; said second speaker being disposed with its radiation axis at an angle of ninety degrees with respect to the radiation axis of the first speaker.

References Cited by the Examiner UNITED STATES PATENTS 2,114,680 4/ 1938 Goldsmith 84-125 X 3,040,613 6/ 1962 Tennes 84-1.25 3,083,606 4/ 1963 Bonham 84-1.25 3,110,801 ll/l963 Katzenstein et al. 307-885 X 3,110,818 11/1963 Sack 332-3 X ARTHUR GAUSS, Primary Examiner.

D. D. FORRER, Assistant Examiner. 

1. A VIBRATO SYSTEM FOR AN ELECTRICAL MUSICAL INSTRUMENT COMPRISING: FIRST AND SECOND SIGNAL CHANNELS; INPUT MEANS FOR A VIBRATO SIGNAL; FIRST PHASE SHIFTING MEANS IN SAID FIRST CHANNEL AND COUPLED TO SAID INPUT MEANS, AND SECOND PHASE SHIFTING MEANS IN SAID SECOND CHANNEL AND COUPLED TO SAID INPUT MEANS, SAID FIRST PHASE SHIFTING MEANS PRODUCING AN OUTPUT SIGNAL IN SAID FIRST CHANNEL DISPLACED IN TIME AHEAD OF THE OUTPUT SIGNAL IN SAID SECOND CHANNEL BY A PREDETERMINED AMOUNT; MEANS PRODUCING A MUSICAL SIGNAL; FIRST MODULATING MEANS IN SAID FIRST CHANNEL AND COUPLED TO SAID FIRST PHASE SHIFTING MEANS AND COUPLED TO SAID MUSICAL SIGNAL PRODUCING MEANS AND PRODUCING A FIRST MODULATED MUSIC SIGNAL; SECOND MODULATING MEANS IN SAID SECOND CHANNEL AND COUPLED TO SAID SECOND PHASE SHIFTING MEANS AND COUPLED TO SAID MUSICAL SIGNAL PRODUCING MEANS AND PRODUCING A SECOND MODULATED MUSIC SIGNAL; PHASE CHANGING MEANS COUPLED TO SAID MUSICAL SIGNAL PRODUCING MEANS AND PRODUCING A MUSIC SIGNAL DELAYED IN TIME WITH RESPECT TO THE MUSIC SIGNAL PRODUCED BY SAID MUSIC SIGNAL PRODUCING MEANS; MATRIX MEANS RECEIVING THE TIME DELAYED MUSIC SIGNAL AND RECEIVING THE SAID FIRST 